Shipwreck Central is an excellent site about exploring shipwrecks and their preservation. It is also home to the Sea Hunters with Clive Cussler (author of many novels, and finder of the Hunley) and James Delgado (archaeologist and author). There is a section for teachers, video of underwater dives, and an ongoing blog. There are plans for a membership site as well.
(( Shipwreck Central ))